Effects of Midazolam on Cerebral Blood Flow in Human Volunteers

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Abstract
The effects of i.v. midazolam on cerebral blood flow were evaluated in 8 healthy volunteers by using the 133Xe inhalation technique. Six minutes after an i.v. dose of 0.15 mg/kg midazolam, the cerebral blood flow decreased significantly (P < 0.001) from 40.6 .+-. 3.3 to 27.0 .+-. 5.0 ml/100 g per min. Cerebrovascular resistance (CVR) increased from 2.8 .+-. 0.2 to 3.9 .+-. 0.6 mm Hg/(ml/100 g per min) (P < 0.001). Mean arterial blood pressure decreased significantly (P < 0.05) from 117 .+-. 8 to 109 .+-. 9 mm Hg, and arterial CO2 tension increased from 33.9 .+-. 2.3 to 38.6 .+-. 3.2 mm Hg (P < 0.05). Arterial O2 tension remained stable throughout the study, 484 .+-. 95 mm Hg before the administration of midazolam and 453 .+-. 76 after. All the subjects slept after the injection of the drug and had anterograde amnesia of 24.5 .+-. 5 min. The decrease in mean arterial blood pressure was probably not important, since it remained in the physiologic range for cerebral blood flow autoregulation. The increase in arterial CO2 tension observed after the midazolam injection may have partially counteracted the effect of this new benzodiazepine on cerebral blood flow. Midazolam might be a safe agent to use for the induction of anesthesia in neurosurgical patients with intracranial hypertension.